.clearfix:before,
.clearfix:after {
  content: "";
  display: table;
  clear: both;
}
* {
  padding: 0;
  margin: 0;
}
.wrap {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  width: 600px;
  height: 600px;
  margin: auto;
}
.wrap #tab {
  list-style: none;
}
.wrap #tab li {
  float: left;
  width: 150px;
  height: 50px;
}
.wrap #tab li:nth-child(1) {
  background-color: #acf;
}
.wrap #tab li:nth-child(2) {
  background-color: #ccc;
}
.wrap #tab li:nth-child(3) {
  background-color: #aaa;
}
.wrap #container {
  position: relative;
}
.wrap #container div {
  position: absolute;
  left: 0;
  top: 0;
  width: 400px;
  height: 400px;
}
.wrap #container div:nth-child(1) {
  background-color: #acf;
}
.wrap #container div:nth-child(2) {
  background-color: #ccc;
}
.wrap #container div:nth-child(3) {
  background-color: #aaa;
}
